But it is also threatening the stability of the Overstrand cliffs, which are frequently slipping into the sea due to erosion. A large cliff slip earlier this year led North Norfolk District Council (NNDC) to block off the Overstrand sea wall. It was later found that this cliff slip contained Japanese knotweed and the work to remove the plant has now been confirmed. A spokesman for NNDC said: "Over the next eight weeks, work will be undertaken to remove the slip material, treat the Japanese knotweed on the cliffs and stabilise the slope." Japanese knotweed can cause damage to buildings and other structures(Image: PA)Weedkiller will be applied to the top and base of the cliff, before a contractor is brought in to remove the Japanese knotweed material from the sea wall.